Vehicle headlamp having a dual-segment reflector

ABSTRACT

A vehicle headlamp having a single concentrated light source and a unitary concave reflector which is contoured to provide a pair of hemiparabolic reflector segments that have axially spaced focal points and merge with one another along a protruding step that extends horizontally along the inner surface of the reflector. The light source extends between and is so oriented relative to the focal points of the reflector segments that the light beams from the segments are superimposed and thus form a single composite beam of intense light that has a sharp horizontal cut-off. A shield mounted in front of the light source intercepts direct rays from the source and prevents glare. The lamp is preferably of &#39;&#39;&#39;&#39;sealed beam&#39;&#39;&#39;&#39; construction and contains a C6 or C8 type filament. Axially or transversely mounted halogenincandescent lamps can also be employed as light sources. The lens component of the lamp is preferably provided with vertically extending flutes to provide additional control of the beam pattern or, alternatively, can be made of clear glass. In the case of a PAR 36 type lamp having a C8 filament or an axially mounted halogen-incandescent lamp, a domed lens is used to accommodate the shield and mount structure. Also disclosed are vehicular roadway-lighting systems wherein one of the aforesaid segmented reflector headlamps is combined with three conventional headlamps to provide low-beam, turnpikebeam, and high-beam modes of illumination-or a pair of segmentedreflector lamps are used as an auxiliary lighting system which supplements the illumination of a conventional headlamp system during passing or when driving in a fog or under similar hazardous driving conditions.

United States Patent Pitkjaan 1 Aug. 29, 1972 [54] VEHICLE HEADLAMP HAVING A DUAL-SEGMENT REFLECTOR [72] Inventor: Elam Pitkjaan, Cedar Grove, NJ.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Oct. 1, 1970 [21] Appl. No.: 77,092

[52] US. Cl ..3l3/l14, 315/82, 240/4125 C, 313/113 [51] Int. Cl ..H01j 5/16 [58] Field of Search .313/113 C, 113, 114; 315/82 C; 240/4125 C [56] References Cited UNITED STATES PATENTS 2,362,172 11/1944 Swanson ..313l110 3,553,519 1/1971 Hicks ..313/113 Primary ExaminerNathan Kaufman Attorney-A. T. Stratton, W. D. Palmer and D. S. Bu leza [57] ABSTRACT A vehicle headlamp having a single concentrated ligh source and a unitary concave reflector which is con-' toured to provide a pair of hemiparabolic reflector segments that have axially spaced focal points and merge with one another along a protruding step that extends horizontally along the inner surface of the reflector. The light source extends between and is so oriented relative to the focal points of the reflector segments that the light beams from the segments are superimposed and thus form a single composite beam of intense light that has a sharp horizontal cut-ofl. A shield mounted in front of the light source intercepts direct rays from the source and prevents glare. The

lamp is preferably of sealed beam construction and contains a C6 or C8 type filament. Axially or transversely mounted halogen-incandescent lamps can also be employed as light sources. The lens component of the lamp is preferably provided with vertically extending flutes to provide additional control of the beam pattern or, alternatively, can be made of clear glass. In the case of a PAR 36 type lamp having a C8 filament or an axially mounted halogen-incandescent lamp, a domed lens is used to accommodate the shield and mount structure.

Also disclosed are vehicular roadway-lighting systems wherein one of the aforesaid segmented reflector headlamps is combined with three conventional headlamps to provide low-beam, turnpike-beam, and high-beam modes of illuminationor a pair of segmented-reflector lamps are used as an auxiliary lighting system which supplements the illumination of a conventional headlamp system during passing or when driving in a fog or under similar hazardous driving conditions.

18 Claims, 22 Drawing Figures PATENTEB M1829 I972 SHEET 1 0F 5 FIG.

SCREEN INVENTOR Elam Pitkjoon a AGENT VEHICLE HEADLAMP HAVING A DUAL- SEGMENT REFLECTOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to reflector-type electric lamps and has particular reference to an improved headlamp for a motor vehicle and to roadway lighting systems for vehicles which incorporate the improved headlamp.

2. Description of the Prior Art As is well known, the headlamp systems now in use on motor vehicles frequently do not provide adequate illumination of the roadway under certain driving conditions, especially when passing or driving on a turnpike at high speeds. Driving through fog or in a rain or snow storm is especially hazardous due to the increased amount and intensity of the glare light which is inherently produced by conventional headlamp systems under such conditions.

The aforementioned problems have persisted down through the years despite strenuous efforts to solve them due to the fact that the affect on the drivers of oncoming vehicles must be taken into account. Thus, they cannot be corrected by simply increasing the beam intensity or brightness of conventional headlamps since this would merely tend to blind the other motorists on the road and further increase the glare intensity when driving under fog or adverse weather conditions. Basically, the solution lies in directing more light onto the roadway and concurrently controlling the light rays in such a manner that glare light is reduced for each mode of illumination provided by the headlamp system. In order to be practical from both a manufacturing and an economical standpoint, the headlamps must be such that they can be made on high-speed lamp-making machines now in use and the power requirements of the headlamp system must obviously be maintained within certain limits. Hence, a headlamp which can be massproduced on such machines and a vehicle headlamp system which will provide maximum illumination of the roadway with a minimum amount of electrical power and glare are required.

The foregoing problems and hazards have prompted various types of modified headlamps and roadway lighting systems. In US. Pat. No. 3,148,301 issued Sept. 8, 1964 to R. W. Johnson, for example, there is disclosed a vehicle headlight which provides both a driving beam and a passing beam by utilizing a unitary reflector having two parabolic-shaped reflecting portions that are offset vertically by a spacer portion. A filament is located at the focal point of each of the reflector portions and a shield is disposed between the vertically spaced filaments so that the light from one of the filaments strikes only one of the reflector portions and the light from the other filaments strikes only the other reflector portion thus providing either a driving beam or a low beam, depending upon which of the filaments is energized.

A similar result is achieved with a single filament in U.S. Pat. No. 3,191,024 issued June 22, 1965 to J. Bardin et a1 by employing a pair of axially spaced parabolic reflector segments, a single filament and a movable parabolic mirror which is rotated through the gap between the two reflector segments to produce a high beam or a low beam, depending upon the position of the movable mirror. A headlamp that has a more efficient reflector component is disclosed in U.S. Pat. No. 3,221,200 issued Nov. 30, 1965 to L. H. Verbeek. The reflector is of unitary construction and defines three parabolic segments that are radially spaced from one another and are each provided with its own lightemitting element, such as a coiled filament or a halogen-incandescent lamp. A vehicle headlamp comprising a segmented reflector which has two vertically and axially spaced focal points, a pair of light sources, and a specially contoured cover plate or lens to reduce glare is disclosed in U.S. Pat. No. 3,375,363 issued Mar. 26, 1968 to J. Rijnders et al.

A tri-beam headlamp system comprising four sealedbeam lamps having conventional parabolic reflectors and single on-focus light sources that are selectively energized to provide a low beam, a turnpike-driving beam and a high beam is disclosed in U.S. Pat. No. 3,373,311 issued Mar. 12, 1968 to K. H. Neulinger et al. A sealed-beam type headlamp having a conventional parabolic reflector and a dome-shaped lens is disclosed in U.S. Pat. 3,413,508 issued Nov. 26, 1968 to E. Pitkjaan, the author of the present invention.

SUMMARY OF THE INVENTION Briefly, the foregoing problems and deficiencies associated with the headlights and road-lighting systems now in use, as well as the higher cost and complicated manufacturing operations entailed in the lamp structures proposed by the prior art, are avoided in accordance with the present invention by combining a single concentrated light source and a shield with a unitary reflector member that is divided by a protruding step along its horizontal axis into two hemiparabolic reflector segments that are optically oriented relative to one another and to the light source in such a manner that they provide two glare-free light beams of substantially equal intensity that are superimposed and form a single composite beam which has a sharp horizontal cut-off. The configuration of the hemiparabolic segments is such that their focal points are spaced from one another along the mechanical axis of the reflector and the light source is so positioned that it extends horizontally between the focal points in substantial alignment with the step. The geometrical and optical relationships of the light source and the focal points are such that the upper reflector segment provides a convergent beam of light and the lower reflector segment provides a divergent beam of light. The beam angles are so correlated that the two beams overlap one another at a predetermined distance in front of the lamp and form a composite beam of light having a controlled beam pattern.

Tests have shown that the composite beam pattern fonned on a screen positioned in front of the improved lamp and normal to its mechanical axis does not exhibit the characteristic bow-tie" beam configuration with a diamond-shaped hot spot in the middle which is produced by conventional headlamps having a single parabolic surface and an on-focus light source. The composite beam has a sharp horizontal cut-off equivalent to that which would be obtained if the lower half of the reflector were shielded. However, the light flux emanating from the lower reflector segment is not wasted but is utilized to increase the intensity of the beam and project more usable light onto the roadway. The composite beam is preferably spread laterally by vertically extending flutes on the lamp lens which provide a generally rectangular beam pattern. Due to its sharp horizontal cut-off, the beam, despite its intensity, drastically reduces the amount of glare light both with respect to oncoming traffic and preceding vehicles compared to conventional headlamps having a single parabolic reflector surface.

Since the reflector is of unitary construction, it can be readily manufactured by glass molding techniques or stamped from sheet metal. The light source, shield, reflector and lens can be assembled in accordance with standard lamp-making procedures on conventional machines thus eliminating the need for special equipment and tedious or expensive manufacturing operations.

Either a conventional coiled refractory wire filament (C6 or C8) or a halogen-incandescent lamp is used as the light source and a dome shaped lens or cover is employed to provide sufficient space to accommodate the shield and light source structure in the case of small size lamps, such as the PAR 36 type.

The sharp horizontal cut-off and higher intensity of the composite beam produced by the improved lamp of the present invention is used to enhance the turnpikedriving beam and high-beam illumination provided by the headlamp system disclosed in the aforementioned Neulinger et al., patent by substituting the improved lamp for their tumpike lamp (lamps 6 and 16 in the patent drawing). In another embodiment, a pair of segmented reflector lamps are employed in combination with a conventional headlamp system to supplement the low-beam illumination during passing and when driving in fog or similar glare-producing weather conditions.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the invention will be obtained from the exemplary embodiments shown in the accompanying drawings, wherein:

FIG. 1 is a schematic representation of the composite non-glare light beam obtained with an axially mounted light source and a dual-segment reflector in accordance with the invention;

FIG. 2 is a cross-sectional view of a unitary dual-segment reflector which embodies the features shown schematically in FIG. 1;

FIG. 3 is a similar view of a modified molded glass reflector and an axially extending light source in accordance with an alternative embodiment;

FIG. 4 is a side elevational view, partly in section, of a PAR 46 type sealed-beam lamp which has a reflector of the type shown in FIG. 3 but utilizes a transversely extending (C6) filament coil as a light source;

FIG. 5(a) is a plan view of another PAR 46 type sealed-beam lamp which includes a shield and is adapted for use as a vehicle headlamp, a portion of the lamp envelope being removed to show the structure of the shield and filament mount assembly;

FIG. 5(b) is an enlarged plan view of the filamentshield assembly and associated reflector portion of the lamp shown in FIG. 5(a);

FIG. 5(0) is a front view of the C6 filament and associated portion of the mount structure showing the spatial relationship of the filament and the vertical and horizontal centerlines of the reflector;

FIG. 6 is a schematic representation of the reflector and horizontally oriented C6 filament combination shown in FIGS. 5(a) to 5(0) and the resulting composite beam pattern;

FIG. 7 is a schematic illustration of an improved tribeam automobile headlighting system utilizing three headlamps which have conventional parabolic reflectors and one lamp which has a dual-segment reflector according to the invention;

FIG. 8 is a circuit diagram of the energizing and switching circuit used in the tri-beam headlighting system shown in FIG. 7;

FIGS. 9a to are isocandle diagrams illustrating the beam patterns produced by a conventional single-fila ment headlamp and segmented reflector headlamps having a clear lens and a fluted lens, respectively;

FIG. 10 is a front elevational view of a fluted lens used in the lamp which provided the beam pattern shown in FIG. 9(6);

FIG. 11 is a schematic representation of an alternative embodiment of the invention wherein a tubular halogen-incandescent lamp is utilized with a dual-segment reflector;

FIG. 12 is a plan view of a PAR 36 sealed-beam reflector lamp having the segmented reflector and halogen lamp combination shown in FIG. 11 as well as a light shield and a specially conformed dome-shaped lens, a portion of the envelope being removed to show the shield and lamp mount assembly;

FIGS. 13(a) and 13(b) are front elevational views and cross-sectional views, respectively, of an alternative dome-shaped lens for a PAR 36 type lamp in accordance with the invention;

FIG. 14 is a front elevational view of an alternative fluted lens embodiment;

FIGS. 14(a) and 14(b) are enlarged fragmentary cross-sectional views of different portions of the fluted lens shown in FIG. 14;

FIG. 15 is a plan view of a PAR 46 type headlamp having a shielded halogen-incandescent lamp and a dual-segment metal reflector that is fitted with a removable glass lens; and

FIG. 16 is a schematic representation of a conventional headlamp lighting system that includes four lamps and is supplemented by an auxiliary headlamp system consisting of two smaller headlamps that are mounted below the main headlamps and embodying the segmented reflector concept of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (FIGS. 1 and 2) In FIG. 1 there is shown a schematic representation of the basic concepts embodied by the present invention. As illustrated, a concave reflector having a top segment R, and a bottom segment R (shown in dashed outline) of hemiparaboloidal configuration is combined with a concentrated elongated light source S that extends along the mechanical axis X-X of the reflector between the focal point F of the top segment and the focal point F of the lower segment to form two beams of light B, and B that are substantially superimposed and provide a composite beam of light B on a screen located a predetermined distance in front of the light source and placed at right angles to the axis X-X. In this particular embodiment the optical axes of the top reflector segment R, and the bottom reflector segment R, are both coincident with the mechanical axis X-X of the dual-surface reflector member so that the respective focal points F, and F, both lie on axis X-X. The bottom reflector segment R,, is offset in a forward direction from the top reflector segment R, and the focal lengths of the segments are substantially equal. Hence, the focal points are spaced a predetermined distance from one another along the longitudinal mechanical axis X- X of the reflector with focal point F, being located closer to the apex of the reflector than focal point F,,.

Since the light source S is located inside focal point F,,, the beam formed by light rays reflected from the bottom reflector segment R, is slightly divergent and forms a generally hemispherical light beam B, on the screen that is centered on the vertical axis V-V and is generally aligned with and extends below the horizontal axis H-H. The screen is located approximately 25 feet in front of the reflector light source combination as is customary when evaluating the beam patterns of vehicle headlamps. In contrast, since the light source S is located slightly beyond or outside of focal point F,, the beam formed by the light rays reflected from the top reflector segment R, is convergent and forms a hemispherical beam of light 8, that substantially overlaps and is slightly smaller than the hemispherical beam 8,, formed by the bottom segment.

The resulting composite beam B, is centered on the screen, has a sharp horizontal cut-off that is generally aligned with the horizontal axis H-H, and does not exhibit the bow-tie beam configuration or diamondshaped hot spot characteristic of conventional headlamps having a single parabolic reflecting surface. The sharp horizontal cut-off obtained is equivalent to that which would be derived by shielding the lower half of a conventional parabolic reflector. However, the dual-segment reflector of the present invention achieves this desirable horizontal cut-off without shielding (and thus without wasting the light from) the lower half of the reflector but adds this light flux to the projected light beam. Composite beam B thus has approximately twice the brightness or intensity of a beam generated by an identical light source and a conventional parabolic reflector with a shielded lower half and, by virtue of the more uniformly controlled distribution of the light flux and absence of a centralized hot spot, produces less glare to on-coming traffic as well as preceding vehicles as compared to a standard parabolic headlamp.

While the elongated light source S is disposed between the foci F, and F, in the embodiment shown in FIG. 1, a controlled composite light beam of suitable intensity and configuration will also be obtained if the light source extends slightly beyond F, and at least three-fourth of the source is located between F, and F,,. Lamps made in this manner are thus within the scope of the present invention.

It is an important feature of the present invention that the two hemiparabolic reflector segments constitute parts of a unitary reflector member 15, such as that shown in FIG. 2. The reflector member is of concave configuration and can be molded from a suitable vitreous material such as glass, as illustrated, or can be stamped from suitable sheet metal. In this particular embodiment, the hemiparabolic top segment 16 has the same shape and focal length as the bottom segment 17 but the latter has a thicker wall dimension and is thus offset in a forward direction relative to the top segment a distance such that a protruding step 18 is formed along the horizontal centerline of the reflector 15 where the two segments merge with one another. THe axial dimension of this step 18, at the apex of the reflector 15, is substantially equal to the distance between focal point F of the top reflector segment 16 and focal point F of the bottom reflector segment 17. The step dimension in this case is substantially the same across the entire diameter of the reflector 15. The rim 19 of the reflector 15 is, however, circular and identical to that of a conventional reflector.

The light source comprises a coiled filament 20 of refractory wire, such as a C8 tungsten filament, that extends between the two focal points along the mechanical axis X-X of the reflector 15. Filament 20 is thus disposed in the focal plane of the reflector 15 and is substantially aligned with and extends in the same general direction as the step 18. The reflector segments 16 and 17 have a common optical axis which coincides with the mechanical axis X-X and the orientation of the filament 20 and the respective reflector segments is such that the angle of beam convergence (angle or) produced by the top segment 16 is approximately equal to the angle of beam divergence (angle B) provided by the bottom segment 17.

As will be noted in FIG. 2, the top reflector segment 16 merges with the trailing edge of step 18 and the bottom offset segment 17 merges with the leading edge of the step.

FIGURE 3 EMBODIMENT The optical axes of the top and bottom segments of the unitary reflector do not have to be coincident with one another or with the mechanical axis of the reflector to achieve a composite beam having the desired features. Moreover, the focal lengths of the reflector segments need not be equal.

This facet of the invention is illustrated in FIG. 3 wherein a modified reflector 15a of molded glass or the like is formed in such a manner that the optical axis 0- O of the bottom reflector segment 17a is tilted downwardly relative to the mechanical axis X-X through a predetermined tilt angle 'y. In addition, the focal length of the bottom segment 17a is greater than that of the top segment 16a so that the spacing between the FOCI F and F is substantially the same as that in the FIG. 2 embodiment. This permits both the wall thickness of the bottom segment 17a and the dimension of the step 18a to be reduced by an amount such that the wall thickness of the bottom segment 17a is approximately the same as that of the top segment 16a. The axial dimension of step 18a, at the reflector apex, is thus less than the spacing between the FOCI.

The optical axis of the top segment 16a is coincident with the mechanical axis X-X of the reflector 15a and thus produces a beam having a convergence angle or equivalent to that in the FIG. 2 embodiment. However, due to the downward tilt of the bottom segment 170, the beam divergence (angle B) effected by this segment is less than that which would be achieved with a nontilted lower segment. The tilt angle 7 and the beam divergence angle B are such that their combined effect is sufficient to produce a downward throw or depression of the light rays reflected by the lower segment 17a which is generally equivalent to the downward throw of light produced by the convergence angle a of the top segment 16a. The contour of the two segments 16a and 17a is such that the axial spacing between the respective focal points F and F is the same as in the FIG. 2 embodiment and the C8 filament 20a is located in the plane that passes through the two focal points. The reduction of the thickness of the bottom segment 17a achieved by the controlled tilting of its optical axis not only reduces the amount of glass required to mold the reflector but prevents strains from occurring in the glass during annealing and thus makes it much easier to make the reflector.

The same advantages can also be obtained without tilting the reflector segments and simply modifying the configuration of the lower reflector segment 17a so that its focal length is greater than that of the upper segment 160. By properly correlating these parameters the desired spacing between focal points and reduction in the step dimension can be obtained without tilting the lower segment, in which case the optical axes of both segments would be coincident with the mechanical axis of the reflector member. Optimum optical efficiency and step reduction is achieved by employing reflector segments that have a common optical axis which is tilted and a bottom segment whose focal length is greater than that of the top segment and this combination of features is preferred in the turnpikebeam lamp application described below.

While a specular coating of aluminum or the like on the concave inner surfaces of the integral vitreous reflectors and 15a has not been shown, it will be understood that such a coating is deposited on such surfaces before the reflectors are manufactured into headlamps.

FIGURE 4 EMBODIMENT A sealed-beam reflector lamp 22 having a unitary reflector 23 that is molded from glass and has a horizontal step 21, a top hemiparabolic reflector segment 24 and a bottom hemiparabolic segment 25 which have a common optical axis which is tilted downwardly through a predetermined angle and have different focal lengths as in the above-described preferred embodiment is shown in FIG. 4. The inner surfaces of the reflector segments 24 and 25 are coated with a layer 26 of suitable specular material such as aluminum that is vapor deposited in the usual fashion. The mouth of the reflector 23 is closed by a light-transmitting cover such as a lens 27 of clear glass that is slightly convex outwardly and has its periphery fused and hermetically sealed to the matching rim of the reflector 23 in accordance with standard lampmaking practice to form an annular bead 28. A pair of rigid lead wires 29 (only one of which is visible in FIG. 4) extend through spaced openings in the back of the reflector 23 and are electrically joined, as by brazing, to a pair of metal ferrules 31 that are hermetically sealed to bosses molded into the exterior surface of the reflector. L-shaped metal terminals 32 are fastened to the respective ferrules 31 to provide a blade-like connector adapted to be inserted into a suitable socket.

The envelope formed by the reflector 23 and lens 27 is evacuated and filled with suitable inert gases, such as a mixture of argon and nitrogen, through a tubulation (not shown) in the usual fashion and the tubulation is then tipped off.

FIGURES 5-6 EMBODIMENT In FIG. 5(a) there is shown a lamp 22a that is of the same basic construction as lamp 22 except that lamp 22a is specifically designed for use as a headlamp. Lamp 22a is thus provided with a concave shield 34 that is mounted in front of and in masking relationship with the C6 filament 30a to intercept direct light rays from the filament that would otherwise pass through the clear glass lens 27a and blind the drivers of on-coming vehicles and those immediately in front of the car being driven. The shield 34 is fabricated from a suitable metal such as nickel-plated iron and is suspended in its filament-masking position by a strap 35 that extends from the shield and is fastened as by spot welding to one of the lead wires 29a.

The envelope formed by the reflector 23a and lens 27a is evacuated and gas-filled through a metal tube 33 that is sealed into the back of the vitreous reflector 23a and communicates with an opening in the reflector. The filament 30a is connected electrically to lug terminals 32a by the lead wires 29a and sealed-in ferrules 31a in the customary fashion. A specular coating 26a is also provided on the inner surface of the dual-segment reflector 23a (only the top segment 24a of which is shown in FIG. 5(a)).

The spatial relationship of the filament 30a and the reflector 23a is shown in the enlarged plan view of the filament mount assembly shown in FIG. 5(b). As will be noted, the centerline C-C of the C6 filament 30a, as viewed in FIG. 5(b), is offset a predetermined distance to the left of the mechanical axis X-X of the reflector 23a so as to deflect the reflected light rays to the right of axis X-X and, hence, to the right of the roadway. In addition, as shown in the front view of the mount assembly depicted in FIG. 5(a), the inner ends of the lead wires 29a are slanted upwardly to position the filament 30a in plane 0-0 that is generally parallel to and spaced a predetermined distance above the horizontal axis Z-Z of the reflector 23a and passes through the focal points of the two reflector segments 24a and 25a (not shown). As shown in this view, the centerline C-C of the filament 30a is offset to the right of the vertical axis Y-Y of the reflector 23a.

The beam pattern produced by the headlamp 22a is illustrated schematically in FIG. b. As shown, the offset of the C6 filament 30a to the left of the longitudinal mechanical axis X-X and upwardly from the horizontal axis Z-Z of the reflector 23a into focal plane O-O produces a generally rectangular beam 36 on a screen 37 that is positioned approximately feet in front of the headlamp and at right angles to the mechanical axis X-X of the reflector. The composite beam 36 formed by the reflected light rays is of uniform intensity and, as will be noted, is located to the right of the vertical axis V-V of the screen and has a sharp horizontal cut-off that maintains practically all of the light flux below the horizontal axis H-I-I of the screen. When mounted on the front of a motor vehicle, lamp 22a would, accordingly, provide an intense beam of light that would be directed downwardly in front of the vehicle and to the right of the roadway and thus produce little or no glare.

As will be noted in FIG. 6, the curvature of the two hemiparabolic reflector segments 24a and 25a is such that their respective focal points F and F are located on opposite sides of the transversely extending filament a and are spaced apart a-distance d that is equal to or only slightly greater than the coil barrel diameter of the filament.

TRI-BEAM I-IEADLAMP SYSTEM ENIBODIMENT (FIGS. 7-8) In FIG. 7 there is shown a schematic representation of a headlamp system comprising the dual-segment reflector lamp 22a of FIGS. 5-6 and three other headlamps 38, of conventional design that can be selectively operated to provide three types or modes of illumination, depending upon driving conditions. The headlamp system shown in FIG. 7 can thus be termed a tri-beam headlamp system which, while similar in some respects to the system disclosed and claimed in the aforementioned Neulinger et al. US. Pat. No. 3,373,31 l, is an improvement over that system.

While the four headlamps may be grouped vertically one above the other in pairs on either side of the centerline of the vehicle, in FIG. 7 they are arranged in a horizontal plane in pairs which are disposed on opposite sides of the centerline. The two outboard lamps 38 provide low-beam illumination and have a single horizontally positioned (C6) filament that is located at the focus of a conventional parabolic reflector. The low-beam lamps 38 are provided with the usual prismatic type lens which provides the light control necessary to obtain the desired low-beam lighting pattern. The dual-segment lamp 22a is the inboard lamp on the right side of the vehicle, as viewed head-on as shown in FIG. 7, and is operated in conjunction with the two low-beam lamps 38 to provide a wider and brighter light beam for turnpike driving. Lamp 22a will, accordingly, be referred to as the tumpike lamp.

The other inboard lamp 40 on the left of the vehicle centerline is similar to the low-beam lamps 38 in that it has a conventional parabolic reflector and an on-focus filament. However, it has a higher wattage rating and a prismatic lens which provides a spot light beaming effect that directs the light along the center of the roadway directly in front of the car. Each of the lamps 22a, 38 and 40 are provided with a filament shield which prevents direct rays from the filament from passing through the lens and producing glare light that would blind the drivers of other vehicles. As an exemplary example of the relative wattages of the respective lamps,

the low-beam lamps 38 may have a nominal rating of 50 watts, the turnpike lamp 22a may also have a nominal rating of 50 watts, and the high-beam lamp 40 may have a nominal rating of 60 watts.

The lamps comprising the headlamp system of FIG. 7 are selectively operated to provide the three different modes of illumination by a suitable energizing and control circuit such as that shown in FIG. 8, which circuit is the same as that disclosed in the aforementioned Neulinger et al., patent. As shown, the circuit includes a two-position instrument panel switch 41 having an arcuate keeper segment 61 and the customary footoperated dimmer switch 42, both of which are shown in their open positions. When the panel switch 41 is pulled out to its first position a, the two outboard lamps 38 are energized by the electrical system of the vehicle thus providing low-beam illumination of the character which is described in the aforesaid Neulinger et al., patent and is thus suited for city driving and in traffic conditions where the use of the turnpike or highbeam modes of illumination would be undesirable.

When the panel switch 41 is in its first position a and the dimmer switch 42 is closed, the dual-segment 50 watt inboard turnpike lamp 22a will be energized and its non-glare beam will be added to the illumination provided by the two low-beam lamps 38.

When driving and traffic conditions are such that a more intense illumination of the roadway is required, the two-position panel switch 41 is pulled out to its second position b which thus energizes the inboard 60 watt high-beam lamp 40 and adds its illumination to the turnpike driving beam provided by the three other lamps 38, 22a which remain energized by virtue of the keeper segment 61 of switch 41 which bridges the two switch terminals a and b.

Restoration of the headlamp system to the low-beam mode of illumination from either the turnpike or highbeam modes is accomplished by simply actuating the foot-operated dimmer switch 42 and returning it to its open position. Since the low-beam lamps 38 remain lit in each of the three different modes, the transition from one lighting mode to another is achieved without any temporary black-outs or jumping effects as disclosed in the aforementioned Neulinger et al., patent.

While lamp 22a of FIGS. Sa-Sc is referred to as constituting the turnpike lamp in the above-described headlamp system, it will be appreciated that any of the other dual-segment headlamps disclosed herein may be used for this purpose.

ISOCANDLE DIAGRAMS (FIG. 9)

The improvement in the beam pattern achieved with the dual-segment reflector headlamps of this invention is illustrated by the isocandle diagrams (or light distribution patterns) of various lamps depicted in FIGS. 9(a) to 9(0). As is apparent from 9(a), the light beam of a conventional sealed-beam lamp having a single onfocus C6 filament, a clear lens, a shield and a standard parabolic reflector has the characteristic bow-tie configuration and a concentrated hot-spot that is located on the horizontal axis H-I-I slightly to the right of the vertical axis V-V.

In contrast, a dual-segment reflector lamp having a shielded C6 filament and a clear glass lens in accordance with the invention provides a beam (FIG. 9b)

which is much more uniform as regards intensity and is centered well below the horizontal axis I-I-I-l and further to the right of the vertical axis V-V. The beam pattern, as shown in FIG. 9C, is broadened laterally into generally rectangular configuration and the light flux more evenly distributed when the aforesaid clear glass lens of the dual-segment lamp is replaced by a lens that is provided with vertically extending flutes that spread the light rays laterally through an angle of about 4. The fluted lens is devoid of any horizontal risers and thus eliminates glare light which would otherwise be produced by such risers. A fluted lens of this type is, accordingly, preferred.

FLUTED LENS (FIG. 10)

A fluted lens having the aforementioned light-modifying characteristics is illustrated in FIG. 10. As shown, the lens 43 comprises a circular plate of glass or other suitable light-transparent vitreous material that has a series of flutes 44 on its surface which extend vertically across the lens face. The flutes are of uniform width and, in the case of a glass lens, are molded into and constitute integral parts of the inner surface of the lens. The desired 4 lateral spread of the light rays passing through the lens has been achieved in the case of a PAR 46 type lamp with flutes that were approximately one-fourth inch (6.35 mm.) wide and had an arcuate cross-section which gave the desired spread of light. Various flute configurations can be used as will be obvious to those skilled in the art. The lens 43 is, of course, dished and thus slightly convex outwardly in accordance with standard lamp-making practice.

FIGURES 1l12 LAMP EMBODIMENTS While all of the lamps described above have been of the sealed-beam variety that contain a bare refractory wire filament, the invention is not limited to such light sources. The aforementioned advantages of light beam superimposition and more uniform light intensity with a sharp horizontal cut-off can also be obtained by using a compact halogen-incandescent lamp as the light source. Such lamps are well known in the art and consist of an elongated quartz envelope that contains a tungsten filament and an atmosphere of a suitable halogen gas, such as bromine or iodine, that triggers a gettering cycle which returns vaporized tungsten from the envelope walls back onto the filament.

A dual-segment reflector lamp having such a light source is shown schematically in FIG. 11 along with the beam pattern which it provides. As will be noted, the reflector is of the same type as previously described and has a top hemiparabolic segment R, and'a bottom hemiparabolic segment R that is axially displaced in a forward direction relative to the top segment. The halogen-incandescent lamp 45 is of tubular configuration and in this embodiment is oriented so that its longitudinal axis is coincident with the mechanical axis X- X of the reflector. The lamp 45 contains a linear filament 46 of coiled tungsten wire that also extends along the mechanical axis X-X of the reflector and the lamp is so positioned relative to the reflector that the filament 46 is located between the focal points F, and F of the top and bottom segments of the reflector, respectively. The embodiment of FIG. 11 thus employs the same principles as the FIG. 1 embodiment except that a halogen-incandescent lamp is used as the concentrated light source. The beams from the top and bottom segments R, and R,, of the reflector are thus superimposed and form a generally semi-circular beam pattern 47 on the screen 37, which beam has a sharp horizontal cutoff and is generally symmetrical about the vertical axis V-V.

A PAR 36 type sealed-beam lamp 22b embodying the combination of a halogen-incandescent lamp and a dual-segment reflector is shown in FIG 12, which is a view looking down onto the lamp through the upper hemiparabolic segment 24b. As in the previous embodiments, the molded glass reflector 23b has its inner surface coated with a suitable specular material 26b and rigid lead-in conductors 29b that are electrically connected to metal ferrules 31b sealed into the back of the reflector 23b extend into the sealed envelope formed by the reflector 23b and the glass lens 27b. The inner ends of the conductors 29b are attached to the outer leads of the axially disposed halogen-incandescent lamp 45 and the coiled tungsten filament 46 of the lamp 45 extends along the reflector axis between the focal points of the reflector segments, as disclosed above. As in the previous lamps designed for use on vehicles, a suitable shield 34b is mounted in front of the light source to avoid glare from direct light rays. In this embodiment, the shield 34b comprises a shallow concave metal member that is attached to the longer one of the lead-in conductors 29b and is of sufficient size to mask both the halogen lamp envelope and its protruding sealed tip 39 since it has been found that they can reflect light rays in such a manner as to constitute point light sources and glare-producing sites.

In contrast to the previous embodiments, the glass lens 27b according to this embodiment comprises a dome-shaped member that has a circular rim 19b and a forwardly extending annular side wall that forms a bezel 48 which is joined to and merges with a slightly convex face 52 of clear glass. The added depth of the lens member 27b afforded by the bezel 48 and the resulting dome-shaped configuration of the lens accommodates the outermost end portion of the shield and lamp mount, as shown. Dome-shaped lenses of this type are, accordingly, required when the light source (whether a bare filament or a halogen-incandescent lamp) is axially mounted and the lamp is of small size. This is particularly true when the lamp is of the PAR 36 size (such as that shown in FIG. 12) and has a diameter of 4% inches (approximately 1 1.4 centimeters).

As indicated in the lower portion of the lens 27b (as viewed in FIG. 12), the bezel portion 48 of the lens can, if desired, be colored with a dispersed colored pigment for example, by an exterior coating 49 of a suitable colored lacquer (denoted by the stippled defect in the drawing) such as an amber-colored lacquer that has good weathering properties. The resulting ambercolored bezel portion 48 of the lamp 22b, when the latter is mounted on a vehicle and energized, will thus serve as an integral safety or marker" light viewable from a position abreast of the vehicle.

The effectiveness of such a marker light can be increased by molding axially extending flutes 50 on the inner surface of the bezel 48, as shown in the upper portion of the lens 27b as viewed in FIG. 12, which flutes will spread the light in a vertical direction. The

flutes 50 can be provided over the entire inner surface of the bezel 48 or can be restricted to the portions thereof that constitute the sides of the lens 27b. Such light-spreading flutes 50 can be employed in combination with an exterior amber-colored coating or other suitable colored material, as indicated by the stippled effect on the upper portion of the bezel 48 as viewed in FIG. 12, or they can be used independently without a coloring material.

Coiled-coil filaments (CC6 or CCS) can also be used as the light source.

ALTERNATIVE LENS EMBODIMENT (FIG. 13)

If desired, a selected portion of the front face of the dome-shaped lens member can be provided with flutes to further minimize the possibility of light rays leaving the headlamp in a direction which would produce glare. Such a fluted lens embodiment 27c is shown in FIGS. 13(a) and 13(b). As will be noted, the glass lens 270 is of the same general type previously described and has a circular rim 19, a bezel portion 51, and a slightly dished front face 53. The upper half of the lens face 53 that covers the top segment of the reflector is provided with a series of vertically extending flutes 54 that are molded into the inner surface of the lens and extend around the periphery of that half of the lens face such that a window 58 of clear glass extends upwardly from the horizontal axis Z-Z of the lens 270 and has an arcuate upper terminus that matches the curvature of the lens face. Hence, any stray light rays that may be reflected through the fluted upper portion of the lens 27c will be spread horizontally and neutralized as far as glare is concerned.

ALTERNATIVE LENS EMBODIMENT (FIG. 14)

When the improved lamp of this invention is intended for use as a fog lamp or as part of an auxiliary headlighting system, as hereinafter disclosed, it may be desirable to increase the lateral spread or throw of the light rays to further reduce the glare effect. This can be readily accomplished by employing a lens 55 of the type shown in FIG. 14 which has vertically extending interior fluting over its entire face. As illustrated, the central part (zone A) of the lens face can be provided with flutes 56 dimensioned and shaped to give about a 4 lateral light spread and the arcuate end segments (zones B) of the lens face can be provided with different type flutes S7 dimensioned and shaped to effect about a 32 lateral spread. The configuration of the flutes 56, 57 are shown in FIGS. l4(a)' and 14(b), respectively. As shown, flutes 56 are of arcuate cross section having a radius of curvature R and a width dimension d. Flutes 57 (FIG. 14 b) are of the same width but are of compound arcuate configuration with a central portion having a radius of curvature R1 and end portions having a smaller radius of curvature r. The flutes 56, 57 can be of the same width (dimension d) and flutes one-fourth inch (6.35 mm.) have given excellent results as regards glare control.

The flutes 44 of the PAR 46 lens 43 (FIG. 10) can be of the same type as the flutes 56 formed on the central zone A of the PAR 36 lens shown in FIG. l4.

FIG. 15 LAMP EMBODIMENT The invention is not limited to headlamps of scaledbeam construction such as those previously described but encompasses headlamps which have a sheet metal reflector that is mechanically fastened to a vitreous lens member to form a housing or enclosure which is not hermetically sealed. A headlamp 22d of this type is shown in FIG. 15 and comprises a dual-segment reflector 23d that is stamped from suitable sheet metal, such as aluminum or the like which has a specular concave surface, and is fastened to a dished lens 27d of glass or other suitable vitreous material. The lens 27d IS AT- TACHED TO AND HELD IN PLACE ON THE MATCHING RIM OF THE REFLECTOR 23d BY A SURROUNDING COLLAR 62 OF METAL OR THE LIKE THAT IS PROVIDED WITH SUITABLE LOCKING MEANS (not shown). THE METAL REFLECTOR 23b HAS A TOP HEMIPARABOLIC SEGMENT AND A BOTTOM HEMIPARABOLIC SEGMENT OF THE CHARACTER DESCRIBED previously although only the top segment 24d is shown in the plan view of the headlamp 22d depicted IN FIG. 15.

A suitable light source such as a halogen-incandescent lamp 45d having a linear tungsten wire filament 46d is axially mounted within the lamp housing on L- shaped lead wires 29d that are attached to the rigid outer leads of the halogen lamp 45d and are rigidly secured to the reflector 23d by bushings 59 of insulating material which are anchored in suitable openings in the rear of the reflector. The lead wires 29d are thus insulated from each other and from the metal reflector 23d by the bushings 59. The outer ends of the lead wires 29d are electrically connected as by soldering to metal contactor elements 60 that serve as the lamp terminals. A shield 34d of shallow concave configuration is fastened as by spot welding to the long lead wire 29d and suspended in front of the halogen lamp 45d to mask direct rays of light from the filament 46d and the tubular lamp envelope that would otherwise pass through the lens 27d. The axially extending filament 46d is disposed between the focal points of the respective reflector segments as In the previously described lamp embodiments While the halogen-incandescent lamp 45d in the FIG. 15 embodiment is held in place within the lamp housing by lead wires 29d that are rigidly coupled to the back of the metal reflector 23d, it will be recognized by those skilled in the art that a suitable socket can be fastened to the back of the reflector 23d and that the halogen lamp 45d can be fitted with a base member adapted to be inserted into the socket to permit a new lamp to be placed within the reflector by removing the locking collar 62 and lens member 27d.

ALTERNATIVE HEADLIGHTING SYSTEM (FIG. 16)

The dual-segment reflector headlamps of the present invention can also be employed as auxiliary headlamps to supplement the illumination provided by conventional four-headlamp lighting systems presently in use on motor vehicles. A schematic representation of such a modified headlighting system is shown in FIG. 16 and comprises a primary headlight system that consists of two outboard lamps 63 and two inboard lamps 64 that are arranged in pairs on opposite sides of the centerline of the vehicle. The two outboard lamps 63 each contain a pair of shielded C6 type filaments, one of which is positioned on-focus with the other positioned slightly above the focal point of the reflector. The two inboard lamps 64 each contain a single on-focus C6 filament that is also shielded. Each of the lamps 63 and 64 are of the conventional type and have non-segmented parabolic reflectors and prismatic lenses that provide the proper optical control of the light rays.

Low-beam illumination is provided in the conventional manner by energizing the on-focus of both outboard lamps 63 and high-beam illumination is provided by energizing both of the inboard lamps 64 in conjunction with the off-focus filaments of both outboard lamps 63. Selective operation of lamps 63 and 64 which comprise the primary headlighting system to provide the aforesaid low-beam and high-beam modes of illumination is accomplished in the usual fashion by a suitable energizing circuit that includes a panel switch and foot-operated dimmer switch.

In accordance with this embodiment of the invention the low-beam mode of illumination provided by the primary headlighting system is supplemented by a pair of auxiliary passing or fog lamps 65 of the dual-segment reflector type which have a single concentrated light source, such as a C6 filament (or preferably a C8 filament), that extends between the focal points of the reflector segments as disclosed previously. The auxiliary lamps 65 are of smaller size than the primary headlamps (preferably PAR 36 type lamps when the primary lamps are PAR 46) and are mounted below each pair of the primary headlamps on opposite sides of the centerline of the vehicle, as shown in FIG. 16.

When driving in fog or in other adverse conditions which tend to increase the reflected glare level, the low-beam illumination provided by the primary headlight system is supplemented by energizing the two auxiliary lamps 65 by means of an energizing circuit that can be independent from, or coupled to, the energizing circuit for the primary headlamps 63, 64. The depressed composite light beams and the sharp horizontal cut-off of the light rays provided by the auxiliary lamps 65 enhances the low-beam illumination of the primary headlight system in such a manner that the roadway in front of the vehicle is illuminated for a much greater distance with a minimum amount of glare. The auxiliary headlamps 65 could, therefore, be coupled with the primary headlighting system in such a way that they are automatically energized along with the low-beam headlamps 63 during passing to project more light further down the roadway during this critical and potentially hazardous driving maneuver.

SPECIFIC EXAMPLES TABLE I spacing step between dimen focal Light Source coil Reflector at coil type dia. angle pts. apex type dia. length PAR36 ll.4cms. None 4.3 mm. 4.3 mm C8 fil 1.5mm 4.5mm PAR36 ll.4cms. 3 4.3 mm. 3.0 mm C8 fil 1.5mm 4.5mm

(bottom seg.) PAR46 l4.6cms. None 4.1 mm. 4.1 mm C8 fil 1.5mm 4.5mm PAR46 14.6cms. 2

bottom seg.) 4.1 mm.3.1 mm C8 fil 1.5mm 4.5mm PAR46 14.6cms. 2 1.9 mm. 1.0 mm C6 fll1.5mm 4.5mm

(both seg.)

When reflector segments having a common tilted optical axis are employed a 2 tilt angle is preferred and tilt angles within a range of 2 to 3 are suitable. When only the bottom segment is tilted, a tilt angle of 3 is preferred but tilt angles within a range of 2 to 5 can also be used.

It will be appreciated from the foregoing that an improved headlamp and various headlighting systems have been provided for motor vehicles which produce a composite beam of light that greatly improves the illumination of the roadway with a minimum of glare. The headlamps are of such construction that they can be readily manufactured on conventional high-speed machines in accordance with standard lamp-making techniques by making small but critical changes in the contour of the reflector member and by properly correlating the configuration, dimensions and location of the light source with respect to the focal points of the respective reflector segments and the mechanical axis of the reflector member per se.

I claim as my invention:

1. A reflector-type electric lamp for producing a composite beam of light having a controlled beam pattern, said lamp comprising the combination of;

a unitary concave reflector having an inner surface which defines a pair of hemiparabolic reflector segments that (a) are offset from one another in an axial direction, (b) merge with one another along a protruding step that extends along the centerline of the reflector and is located on the inner surface thereof, and (c) have focal points that are spaced from one another along the mechanical axis of said reflector, and

a single concentrated light source of elongated configuration supported between the focal points of said hemiparabolic reflector segments and substantially disposed in a plane that passes through said focal points and extends in substantially the same direction as said step so that the light rays from the respective reflector segments are concentrated into two beams of light of substantially equal intensities that are superimposed.

2. The refletor-type electric lamp of claim 1 wherein a vitreous light-transmitting cover is attached to said reflector and together therewith forms a housing that contains said light source.

3. The reflector-type electric lamp of claim 2 wherein the optical axis of at least one of said hemiparabolic reflector segments is tilted with respect to the mechanical axis of said reflector.

4. The reflector-type electric lamp of claim 2 wherein;

said hemiparabolic reflector segments have substantially equal focal lengths and a common optical axis that is substantially coincident with the mechanical axis of said reflector, and

the axial dimension of said step, at the apex of the reflector, is substantially equal to the axial distance between the focal points of the respective reflector segments. 5. The reflector-type electric lamp of claim 2 wherein;

said hemiparabolic reflector segments have different focal lengths and a common optical axis that is substantially coincident with the mechanical axis of the reflector, and the axial dimension of said step, at the apex of the reflector, is less than the axial distance between the focal points of the respective reflector segments. 6. The reflector-type electric lamp of claim 2 wherein;

the hemiparabolic reflector segment that merges with the trailing edge of said step has an optical axis which is substantially coincident with the mechanical axis of the reflector, the other of said hemiparabolic reflector segments has an optical axis that is tilted toward and intersects the mechanical axis of the reflector at a preselected point in front of said reflector, said reflector segments have substantially equal focal lengths, and the axial dimension of said step, at the apex of said reflector, is less than the axial distance between the focal points of the respective reflector segments. 7. The reflector-type electric lamp of claim 2 wherein;

said hemiparabolic reflector segments have a common optical axis that is tilted toward and intersects the mechanical axis of the reflector at a preselected point in front of said reflector, the focal length of the reflector segment which merges with the leading edge of said step is greater than that of the other reflector segment, and the axial dimension of said step, at the apex of said reflector, is less than the axial distance between the focal points of the reflector segments. 8. The reflector-type REFLECTOR-type electric lamp of claim 2 wherein;

said lamp comprises a headlamp for a vehicle, the step defined by the offset reflector segments is substantially horizontal when the headlamp is oriented in its position of use on a vehicle, the reflector segment which merges with the leading edge of said step is offset forwardly and comprises the bottom segment of said reflector when said headlamp is oriented in its position of use, and a shield is mounted within the housing in front of said light source, said shield being of a size and configuration such that it masks the light source and intercepts direct light rays therefrom that would otherwise pass through the light-transmitting cover of the housing. 9. The headlamp of claim 8 wherein; said light source comprises a coiled refractory wire filament of linear configuration that is supported between the focal points of the respective reflector segments by rigid lead-in conductors that extend through the rearward portion of the reflector, and

a pair of exposed terminals are disposed on the back of said reflector and connected to the respective lead-in conductors.

10. The headlamp of claim 9 wherein said coiled linear filament is disposed between the focal points of the respective reflector segments with its longitudinal axis extending transversely across the mechanical axis of said reflector.

l l. The The headlamp of claim 9 wherein;

saidunitary reflector comprises a glass member that has a coating of specular material on its inner surface,

said light-transmitting cover comprises a shallow outwardly dished glass lens that has a periphery which matches that of the glass reflector member, and

said lens and reflector member are hermetically sealed along their peripheries and the lamp thus comprises a sealed-beam type headlamp.

12. The sealed-beam headlamp of claim 1 1 wherein;

the reflector segment that is disposed below the mechanical axis of the reflector, when the headlamp is oriented in its position of use on a vehicle, is offset in a forward direction relative to the upper reflector segment, and

the spatial relationship of said coiled filament and focal points is such that the angle of beam divergence produced by the bottom reflector segment is substantially equal to the angle of beam convergence produced by the top reflector segment.

13. The sealed-beam headlamp of claim 1 1 wherein;

said hemiparabolic reflector segments have substantially the same focal length,

the reflector segment that is disposed below the mechanical axis of the reflector, when the headlamp is oriented in its position of use on a vehicle, and thus constitutes the bottom reflector segment is offset in a forward direction relative to the top reflector segment a distance such that the thickness of said step, at the apex of the reflector, is less than the axial distance between the respective focal points,

the optical axis of said bottom reflector segment is tilted downwardly relative to the mechanical axisof the reflector, and

the optical axis of said top reflector segment is substantially coincident with the mechanical axis of the reflector.

14. The sealed-beam headlamp of claim 11 wherein;

said hemiparabolic reflector segments have a common optical axis that is tilted downwardly toward the mechanical axis of said reflector,

the bottom reflector segment has a focal length that is longer than that of the top reflector segment, and

said coiled linear filament comprises a C6 type filament that is offset to the left and disposed above the mechanical axis of the reflector, when the headlamp is viewed along the direction in which it is aimed during use on a vehicle, so that the resulting composite light beam is depressed and directed to the right relative to the mechanical axis of the reflector when the headlamp is energized and viewed along the aforesaid direction.

15. The headlamp of claim 8 wherein;

said light source is of linear configuration and is supported in axially extending position between the focal points of the respective reflector segments by a mount assembly that includes a pair of rigid leadin conductors that are anchored to the rearward portion of the reflector, and said light-transmitting cover comprises a generally dome-shaped vitreous lens that has an axially protruding bezel portion which accommodates the outermost end of said mount assembly. 16. The headlamp of claim 15 wherein the protruding bezel portion of said vitreous lens includes a dispersed pigment which modifies the color of the light 0 that extend over only the peripheral part of the lens face and defines an upwardly extending window of clear vitreous material. 

1. A reflector-type electric lamp for producing a composite beam of light having a controlled beam pattern, said lamp comprising the combination of; a unitary concave reflector having an inner surface which defines a pair of hemiparabolic reflector segments that (a) are offset from one another in an axial direction, (b) merge with one another along a protruding step that extends along the centerline of the reflector and is located on the inner surface thereof, and (c) have focal points that are spaced from one another along the mechanical axis of said reflector, and a single concentrated light source of elongated configuration supported between the focal points of said hemiparabolic reflector segments and substantially disposed in a plane that passes through said focal points and extends in substantially the same direction as said step so that the light rays from the respective reflector Segments are concentrated into two beams of light of substantially equal intensities that are superimposed.
 2. The reflector-type electric lamp of claim 1 wherein a vitreous light-transmitting cover is attached to said reflector and together therewith forms a housing that contains said light source.
 3. The reflector-type electric lamp of claim 2 wherein the optical axis of at least one of said hemiparabolic reflector segments is tilted with respect to the mechanical axis of said reflector.
 4. The reflector-type electric lamp of claim 2 wherein; said hemiparabolic reflector segments have substantially equal focal lengths and a common optical axis that is substantially coincident with the mechanical axis of said reflector, and the axial dimension of said step, at the apex of the reflector, is substantially equal to the axial distance between the focal points of the respective reflector segments.
 5. The reflector-type electric lamp of claim 2 wherein; said hemiparabolic reflector segments have different focal lengths and a common optical axis that is substantially coincident with the mechanical axis of the reflector, and the axial dimension of said step, at the apex of the reflector, is less than the axial distance between the focal points of the respective reflector segments.
 6. The reflector-type electric lamp of claim 2 wherein; the hemiparabolic reflector segment that merges with the trailing edge of said step has an optical axis which is substantially coincident with the mechanical axis of the reflector, the other of said hemiparabolic reflector segments has an optical axis that is tilted toward and intersects the mechanical axis of the reflector at a preselected point in front of said reflector, said reflector segments have substantially equal focal lengths, and the axial dimension of said step, at the apex of said reflector, is less than the axial distance between the focal points of the respective reflector segments.
 7. The reflector-type electric lamp of claim 2 wherein; said hemiparabolic reflector segments have a common optical axis that is tilted toward and intersects the mechanical axis of the reflector at a preselected point in front of said reflector, the focal length of the reflector segment which merges with the leading edge of said step is greater than that of the other reflector segment, and the axial dimension of said step, at the apex of said reflector, is less than the axial distance between the focal points of the reflector segments.
 8. The reflector-type electric lamp of claim 2 wherein; said lamp comprises a headlamp for a vehicle, the step defined by the offset reflector segments is substantially horizontal when the headlamp is oriented in its position of use on a vehicle, the reflector segment which merges with the leading edge of said step is offset forwardly and comprises the bottom segment of said reflector when said headlamp is oriented in its position of use, and a shield is mounted within the housing in front of said light source, said shield being of a size and configuration such that it masks the light source and intercepts direct light rays therefrom that would otherwise pass through the light-transmitting cover of the housing.
 9. The headlamp of claim 8 wherein; said light source comprises a coiled refractory wire filament of linear configuration that is supported between the focal points of the respective reflector segments by rigid lead-in conductors that extend through the rearward portion of the reflector, and a pair of exposed terminals are disposed on the back of said reflector and connected to the respective lead-in conductors.
 10. The headlamp of claim 9 wherein said coiled linear filament is disposed between the focal points of the respective reflector segments with its longitudinal axis extending transversely across the mechanical axis of said reflector.
 11. The The headlamp of claim 9 wherein; said Unitary reflector comprises a glass member that has a coating of specular material on its inner surface, said light-transmitting cover comprises a shallow outwardly dished glass lens that has a periphery which matches that of the glass reflector member, and said lens and reflector member are hermetically sealed along their peripheries and the lamp thus comprises a sealed-beam type headlamp.
 12. The sealed-beam headlamp of claim 11 wherein; the reflector segment that is disposed below the mechanical axis of the reflector, when the headlamp is oriented in its position of use on a vehicle, is offset in a forward direction relative to the upper reflector segment, and the spatial relationship of said coiled filament and focal points is such that the angle of beam divergence produced by the bottom reflector segment is substantially equal to the angle of beam convergence produced by the top reflector segment.
 13. The sealed-beam headlamp of claim 11 wherein; said hemiparabolic reflector segments have substantially the same focal length, the reflector segment that is disposed below the mechanical axis of the reflector, when the headlamp is oriented in its position of use on a vehicle, and thus constitutes the bottom reflector segment is offset in a forward direction relative to the top reflector segment a distance such that the thickness of said step, at the apex of the reflector, is less than the axial distance between the respective focal points, the optical axis of said bottom reflector segment is tilted downwardly relative to the mechanical axis of the reflector, and the optical axis of said top reflector segment is substantially coincident with the mechanical axis of the reflector.
 14. The sealed-beam headlamp of claim 11 wherein; said hemiparabolic reflector segments have a common optical axis that is tilted downwardly toward the mechanical axis of said reflector, the bottom reflector segment has a focal length that is longer than that of the top reflector segment, and said coiled linear filament comprises a C6 type filament that is offset to the left and disposed above the mechanical axis of the reflector, when the headlamp is viewed along the direction in which it is aimed during use on a vehicle, so that the resulting composite light beam is depressed and directed to the right relative to the mechanical axis of the reflector when the headlamp is energized and viewed along the aforesaid direction.
 15. The headlamp of claim 8 wherein; said light source is of linear configuration and is supported in axially extending position between the focal points of the respective reflector segments by a mount assembly that includes a pair of rigid lead-in conductors that are anchored to the rearward portion of the reflector, and said light-transmitting cover comprises a generally dome-shaped vitreous lens that has an axially protruding bezel portion which accommodates the outermost end of said mount assembly.
 16. The headlamp of claim 15 wherein the protruding bezel portion of said vitreous lens includes a dispersed pigment which modifies the color of the light transmitted by said bezel portion.
 17. The headlamp of claim 15 wherein the protruding bezel portion of said lens has a smooth outer surface and a plurality of integral light-bending flutes disposed on its inner surface.
 18. The headlamp of claim 15 wherein the face portion of said dome-shaped lens that covers the top hemiparabolic segment of said reflector has a plurality of integral light-bending elements on its inner surface that extend over only the peripheral part of the lens face and defines an upwardly extending window of clear vitreous material. 